d15b7

just a point of info -- i have used 100LL AV Gas in my Lotus Super Seven since 1999. never had a 'gas related' engine failure. my motor is a 1600 Ford xflow, high compression (12:1), dual DCOE 40 Webers, Elgin cam, head work, etc. about 170 hp. i've had one failure in the motor - the timing chain broke. i can't see how that would have been caused by AV Gas. just my experience with 100LL.

Todd
PS it's just under $5 a gal where i bought it last week. (tiny little airport)

winders

Todd,

What's the rev limit of that engine?

Scott

mark kibort

I see where you are going with that. It is interesting to me that there is possiblity that some fuels have a rapid burn rate formula, as well as high octane. Im sure, for the type of fuel, this is true. I've still been told that for a given fuel blend, octane can slow the rate of flame front propagation.

anyway, I wonder if there is some truth to the flame front speed of av gas vs racing gas, energy potential differences , and this all pointing to incompatability with high reving engines (say 10,000rpm plus)
The race bike guys use av gas, and dont seem to have any issues

so many factors. who knows the real answers! after reading the two guys from the same company, saying totally opposite thing, I dont know who to believe now.

Mark

d15b7

hi scott.

i typically shift it at 6500-7000 when i am racing (its a vintage car and i care for it). and i was told by the engine builder that if i shifted before 7k, that it would last 'a long time'). it was dynoed out to 7800, and i have on occasion taken it to 7500 (it pulls very strong up there!). this xflow still has the cast crankshaft (balanced and lightened and chamfered and etc etc); if it had a steel Faringdon or Cosworth crank, i could take it to 8k all day long (its already got forged rods and pistons and dual valve springs and steel rocker arm assy, etc).

Todd

SundayDriver

As another reference point, there are quite a few DSR racers who use LL Avgas. 1000cc motorcycle engines reving to 13,000 rpm with no ill effects. Generally they seem to be competitive, power wise, with cars running 'proper' race fuel.

Bill Lehman

Back in the day, Champion Sparkplugs sponsored the SCCA Run-offs. I was running a very high compression MGB on Avgas. The Champion techs gave me a fresh set of plugs before each practice session, I ran a few laps, killed the engine and pulled the plugs for the tech's examination. After the initial test, small beads of aluminum were found on the insulator. The mixture was gradually enriched until this went away. The engine lasted another year.

Plavan

Now for the real question. Can I use Wild Turkey in my tank??? Does it have a high burn rate?

mark kibort

I think some funny car run that.

winders

I hope these guys tune their engines for the aviation fuel. Otherwise, they are likely running lean. When I was racing bikes, a few guys tried running aviation fuel without checking the air/fuel mixture. Some of them had expensive engine rebuilds because of it. Some of the 600cc guys lost as much as 8 hp on the dyno with aviation fuel after adjusting the air/fuel ratio. I can only assume the fuel burned too slowly for their peak RPM.

If aviation fuel was so good, EVERYONE would be using it.

Scott

mark kibort

That is interesting, because Ive seen the write ups of dyno tests where there were no losses. I guess if there is no gains, and some of the risks of tuning, probably not worth the effort to save 20-50 bucks a weekend.

However, i think additing it to pump gas might be a cheap and safe alternative.
wasnt the weight per gallon only about 3-5% less? 5.9 to 6.1 lbs or something?

I dont like the "everyone" testimonial. I think there is a lot of things that some folks do, that no one else does that works well, and sometimes better than conventional thinking or process.

winders

Mark,

First, would you start quoting properly! Putting your comments above a quote is a pain to read.

Second, if aviation fuel was as good as racing fuel and cost ~30% less, it would not be a secret only a few people knew about. Aviation fuel is designed for a different application, period. I live a mile a way from a small aircraft airport and have easy access to aviation fuel. I'd be using it if it were as good as racing fuel!

Scott

mark kibort

You are a demanding little guy, arent you!

So, if aviation fuel is such a different formulation, and such a problem, then I wonder why Steve Poole, the guy that worked with Wusz at 76, said it was the same stuff. I certainly dont know, and you seemed to have all the answers.

there is enough doubt here, that i think if i really wanted to up my octane, i would use it. come to think of it. since I cant get my fuel mixtures any leaner, maybe its good way for me to get from 11:1 to 12:1 and pick up some power. (ive been drowning the motor for a couple of years now at 11:1 AFR and most think that is costing some decent power)

rlm328

Has everyone on this thread completely forgot about basic chemistry and physics. It is about the stoichiometric ratio, or how efficiently a fuel burns. The more carbon and O2 the more efficient it is. here is a link to learn more.

http://www.brighthub.com/engineering...les/15235.aspx

The higher octane prevents pre-detenation or knock. In hot humid areas the radiator does not cool as well as it should, so over hot combustion chambers can lead to bad things happening in ones engine. Alcohol burns much cooler and takes a lot more of it to give the same carbon loading of gasoline, ergo cooler engine temps.

M3EvoBR

High Prices ?
E85 anyone ???

The cheapest race fuel available around.

Veloce Raptor

And this is exactly why I sometimes use it...as I clearly stated much earlier in this thread...to the total befuddlement of our village idiot (not you, RLM).